Population estimates are one of the major outputs of any National Statistical Office. They are key statistics for a wide range of planning and policy decisions and while population can be simply defined e.g. 'the total number of persons inhabiting a country, town or any district or area' (Macquarie Dictionary, 2005) the concepts associated with its measurement are increasingly complex.

In the Australian context the key population measure is the estimated resident population (ERP) which is based on the concept of usual residence. However there are a range of other population concepts that are relevant to different analytical situations. These can include the population in a particular area at a particular time, or, while not entirely consistent with above definition, it can extend to the concept of the population serviced by a particular area.

The objectives of this paper are to discuss the range of population concepts, highlight the differences between the various concepts and identify some of the measurement issues associated with the different concepts.

SCOPE

For the purposes of this paper the following population concepts have been identified and considered:

Population present - based on where people are at a particular point in time i.e. place of enumeration;

Usually resident population - based on where people are usually resident using a range of criteria;

Legal population - based on citizenship and residency permits;

Economic population - based on economic concept of residence;

Working population - based on place of employment;

Service populations - based on demand for and use of services in a particular area.

Each of these concept is discussed briefly below and in more detail in the following chapters.

POPULATION CONCEPTS

The five yearly Census of Population and Housing is the primary source of basic population statistics, providing a total count of the population on census night. Population count may be required on a place of enumeration (de facto) basis as well as on a place of usual residence (de jure) basis (United Nations, 1998a). Importantly the Australian Census can provide population counts on a place of enumeration on census night basis or a place of usual residence basis. It can also provide counts of the working population.

A 'population present' count is the simplest form of population count from a population census, in which people are counted at their place of enumeration (i.e. where they spend census night).

A usual resident count is a count of all usual residents of an area at the time of the census. It counts people where they usually live. The estimated resident population (ERP) is based on census usual residence counts with required adjustments, and is normally higher than the census count at the national level. It refers to all people, regardless of nationality or citizenship, who usually live in Australia.

The legal population of Australia consists primarily of people with Australian citizenship. The legal population based on citizenship criteria is likely to be lower than the ERP, as many segments of the ERP, such as permanent residents and long-term visitors from overseas (including students) are not covered in the legal population. However, Australian citizens overseas (who may not be included in ERP) could form part of the legal population.

The concept of predominant centre of economic interest applies to the definition of an economic population. The concept recommends that a person be considered a resident of the economic territory with which he/she has the strongest links. For most cases, this would be approximated using the practical method of residence for one year or more. However, there are some exceptions which are discussed in the paper.

The concept of a working population relates to persons working and allocates them to the geographic area where they work. There is a limitation in the working population in that it does not account for school, tertiary and other students, and other persons not in employment.

The concept of service populations refers to the population accessing the services of a particular area and may include permanent or temporary residents of the area where the service is sought, or there may be regular and irregular daytime visitors (including commuters), or overnight or short-term visitors to the area.

The increasing mobility of the Australian population and use of population for resource distribution has created a growing demand for service population estimates at the local area level e.g. SLA. The ERP alone does not meet all information needs of users, as some services are also provided to persons who are not usual residents of a particular area. In recognition of the rising interest in the service population, various definitions, conceptual clarifications of the service population, and issues associated with them are discussed in this paper.

Next steps

The paper addresses the different population concepts, however, as noted there are a range of measurement issues. For example, there is no established standard method for determining or estimating the size of a service population of a geographic area or the Australian diaspora. Therefore further research needs to be undertaken into the feasibility of developing frameworks for estimating a service population of geographic areas within Australia and the Australian diaspora.

The ABS is interested in discussing with stakeholders the need for these types of estimates, their application in policy and program formulation, monitoring and decision making, and related matters to help formulate future directions in this statistical field. The ABS would welcome any comments on the matters discussed in this information paper. These may be sent to:

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